The disclosure of Japanese Patent Application No. 2000-215641 filed on Jul. 17, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a vehicle traction control system and more specifically to a traction control system and a method for suppressing a driving slip of a driving wheel by cutting supply of fuel to an engine.
2. Description of Related Art
As one of traction control systems for suppressing a driving slip of a driving wheel in a vehicle such as an automobile, there is a known traction control system for cutting supply of fuel to an engine when the driving slip of the driving wheel becomes excessively large to reduce output torque of the engine and for prohibiting cutting of fuel supply for a predetermined time after execution of cutting of fuel supply as described in Japanese Patent Laid-open No. HEI8-49579, for example.
According to the aforementioned traction control system, because the driving torque of the driving wheel is reduced by cutting the fuel supply to the engine when the driving slip of the driving wheel becomes excessively large, it is possible to effectively suppress the driving slip of the driving wheel. In addition, cutting of fuel supply is prohibited for the predetermined time, after execution of cutting of fuel supply. Therefore, it is possible to effectively prevent repeated execution of cutting of fuel supply and occurrence of a problem such as an excessive rise in temperature of a catalyst due to combustion of unburned components of fuel in an exhaust gas purifying catalytic converter.
However, in the aforementioned traction control system, cutting of fuel supply is prohibited for the predetermined time after execution of cutting of fuel supply. Therefore, even if the driving slip of the driving wheel becomes excessively large and behavior of the vehicle becomes unstable in a condition in which the vehicle is turning after the driving slip of the driving wheel becomes excessively large in straight traveling of the vehicle and cutting of fuel supply is executed, for example, cutting of fuel supply is not carried out until the predetermined time passes. Therefore, it is difficult to suppress the driving slip of the driving wheel and in some cases it is not possible to effectively stabilize the behavior of the vehicle at an early stage.
It is an object of the invention to reliably prevent worsening of behavior of a vehicle by cutting of fuel supply while preventing occurrence of a problem such as an excessive rise in temperature of an exhaust gas purifying catalyst by taking into consideration a possibility that behavior of the vehicle becomes unstable in addition to the aforementioned condition for starting traction control.
A first aspect of the invention is a vehicle traction control system comprising: a driving slip judging unit that judges a degree of driving slip of a driving wheel; a behavior judging unit that judges if there is a possibility that behavior of a vehicle becomes unstable; an executing unit that executes cutting of fuel supply to an engine so as to control the driving slip of the driving wheel when the degree of the driving slip judged by the driving slip judging unit is equal to or greater than a reference value and it is judged by behavior judging unit that there is the possibility that behavior of the vehicle becomes unstable; and a prohibiting unit that prohibits cutting of fuel supply to the engine for a predetermined time after execution of the cutting of fuel supply.
A second aspect of the invention is a method for controlling vehicle traction including: a slip judging step for judging if a degree of driving slip of a driving wheel is equal to or greater than a reference value; a first behavior judging step for judging if there is a possibility that behavior of a vehicle becomes unstable; an executing step for executing cutting of fuel supply to an engine when the degree of the driving slip is judged at the slip judging step to be equal to or greater than the reference value and it is judged at the first behavior judging step that there is the possibility that behavior of the vehicle becomes unstable; and a prohibiting step for prohibiting cutting of fuel supply to the engine for a predetermined time after execution of the cutting of fuel supply.
According to the above system or method, cutting of fuel supply to the engine is executed when it is judged that the degree of the driving slip of the driving wheel is equal to or greater than the reference value and that there is a possibility that behavior of the vehicle becomes unstable. Therefore, the cutting of fuel supply is not executed only because the driving slip of the driving wheel has become large. Therefore, the cutting of fuel supply is reliably executed when the possibility that behavior of the vehicle becomes unstable is then generated in a state in which the driving slip of the driving wheel is large, thereby worsening of behavior of the vehicle is reliably prevented.